Pulse width query in real time

Lynxmotion Electronics & Software
1

Hi Everyone,

I would like to have a cheap and effective way of getting a realtime plot of position (and velocity) versus time of my servo as it moves.

I have found that large loading, which will be common in my project significantly slows down my servo speeds.

I am by no means an expert in servos and the SSC-32, but here are a few ideas I have been tossing around…

  1. QP command to SSC-32.
    a) Any idea what maximum sampling frequency I would get with QP???
    b) Can I space QP samples by an consistent and equal time interval??? How would I do this???

  2. Optical Encoder wheels with the input connected to the SSC-32 input ports A-D or a DAQ

  3. Openning a servo and connecting the PulseWidth feedback to a DAQ and calculating the position? (I think this is just an overcomplicated version of 1)

Any better ideas or comments???

Stuart

2

QP is only reporting the commanded position, not the true position. So if you tell the SSC32 to do a timed move, it will issue a sequence of positions that the servo should follow, but the SSC32 never knows the actual position of the servo.

Option 2 sounds promising, but I’ve never played with the encoders so I can’t give much advice.

Option 3 I think you mean reading the potentiometer value. You can do this with an ADC, HiTecs regulate their pots to something like 2.4 volts so you don’t need any dividers.

Option 4 OpenServo